From December 1986 to June 1987, we had seen four cases of MLD. Diagnosis was based on clinical and laboratory examinations; three were in late infantile and one in juvenile form. The first manifestation of late-infantile of case 1,2 and 3 appeared between 10 months to 17 months after birth. Their developmental milestones prior to the onset had been quite normal. The first symptoms consisted of mental regression, irritability, ataxia, uncoordinated movements or gait disturbance. Later, mental deterioration became obvious, speech was impaired, hypertonicity occured, deep tendon reflexes were diminished. Case 1 became bedridden, quadreplegic, developed optic atrophy and eventually died at the age of four years and four months from pneumonia. Case 4, with a juvenile form of MLD, showed the same clinical features but the onset was later and the clinical course was more protracted. The establishment of diagnosis was based on low serum level of arysulfatase A and delayed nerve conduction velocities.